Optical sensing patches have conventionally been provided for the detection/measurement of oxygen, carbon dioxide and pH. Multilayered oxygen and pH sensing patches are currently sold which, for example, have either a glass or polyester substrate film, upon which is deposited a layer of silicone rubber impregnated with a fluorescent indicator that undergoes oxygen dependent quenching resulting in a reduction in the fluorescence lifetime and emission intensity. Conventional pH sensing patches also use polyester substrates, on which is deposited a hydrogel layer containing a fluorescent pH sensitive indicator.
Some conventional patches are affixed to the inner wall of the container of interest by use of an adhesive that is applied to the patch substrate by the end user. Other conventional oxygen and pH sensing patches have a multilayer design, with a polyester substrate. However, these patches are supplied with an adhesive layer in a peel and stick type format.
Most conventional optical sensing patches disadvantageously require adhesives to attach the sensing film. This use of adhesives creates the potential for delamination when used with polyolefin surfaces (e.g., polypropylene and polyethylene), such as are commonly used as the inner layer of disposable bag-type bioreactors. The polyolefin inner layers of these disposable bag-type bioreactors are important because they impart high biocompatibility and an ability to use heat sealing in the construction of the bag. Further, polyolefins are considered low energy surfaces which lack chemical functional groups that might normally be used to covalently couple with an adhesive layer. For these reasons, cyanoacrylate, epoxy, polyurethane, silicone, and most acrylic adhesives do not adhere to polyolefins.
Conventional optical sensing patches, which utilize direct deposition of the pH sensing hydrogel layer onto a polyester substrate film, are also easily damaged. In particular, while the polyester substrate does provide the hydrogels with a degree of mechanical support, it fails to protect against damage due to handling or abrasives in the solutions to be monitored.
In view of the above-described disadvantages encountered with conventional optical sensing patches, it is an object of the present invention to provide an optical sensing patch capable of effectively bonding to the inner layer of bag bioreactors.
It is a further object of the present invention to provide an optical sensing patch which is durable and resistant to damage. In particular, it is an object of the present invention to provide an optical sensing patch which provides significantly enhanced protection against damage to the sensing composite, by providing a robust scaffold upon which the sensing composite can be deployed.